lacrimal bone

bone (bōn)

1. the hard, rigid form of connective tissue constituting most of the skeleton of vertebrates, composed chiefly of calcium salts.

2. any distinct piece of the skeleton of the body.

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ankle bone  talus.

basiotic bone  a small bone in the fetus between the basilar process and the basisphenoid.

brittle bones  osteogenesis imperfecta.

cancellous bone  see lamellar b.

capitate bone  the bone in the distal row of carpal bones lying between the trapezoid and hamate bones.

carpal bones  the eight bones of the wrist (carpus), including the capitate, hamate, lunate, pisiform, scaphoid, trapezoid, and triquetral bones and the trapezium.

cartilage bone  bone developing within cartilage, ossification taking place within a cartilage model.

cheek bone  zygomatic b.

collar bone  clavicle.

compact bone  see lamellar b.

cortical bone  the compact bone of the shaft of a bone that surrounds the marrow cavity.

cuboid bone  a bone on the lateral side of the tarsus between the calcaneus and the fourth and fifth metatarsal bones.

cuneiform bone, intermediate  the intermediate and smallest of the three wedge-shaped tarsal bones located medial to the cuboid and between the navicular and the first three metatarsal bones.

cuneiform bone, lateral  the most lateral of the three wedge-shaped tarsal bones located medial to the cuboid and between the navicular and the first three metatarsal bones.

cuneiform bone, medial  the medial and largest of the three wedge-shaped tarsal bones located medial to the cuboid and between the navicular and the first three metatarsal bones.

ethmoid bone  the cubical bone located between the orbits and consisting of the lamina cribrosa, the lamina perpendicularis, and the paired lateral masses.

flat bone  one whose thickness is slight, sometimes consisting of only a thin layer of compact bone, or of two layers with intervening cancellous bone and marrow; usually curved rather than flat.

frontal bone  a single bone that closes the anterior part of the cranial cavity and forms the skeleton of the forehead; it is developed from two halves, the line of separation (the frontal suture) sometimes persisting in adult life.

funny bone  the region of the median condyle of the humerus where it is crossed by the ulnar nerve.

hamate bone  the medial bone in the distal row of carpal bones.

heel bone  calcaneus.

hip bone  the large bone in the hip, consisting of the ilium, the ischium, and the pubic bone.

hyoid bone  a horseshoe-shaped bone at the base of the tongue, just superior to the thyroid cartilage.

incisive bone  the portion of the maxilla bearing the incisors; developmentally, it is the premaxilla, which in humans later fuses with the maxilla, but in most other vertebrates persists as a separate bone.

innominate bone  hip b.

jaw bone  the mandible or maxilla, especially the mandible.

jugal bone  zygomatic b.

lacrimal bone  a thin scalelike bone at the anterior part of the medial wall of the orbit, articulating with the frontal and ethmoid bones and the maxilla and inferior nasal concha.

lamellar bone  the normal type of adult bone, organized in layers (lamellae), which may be parallel (cancellous b.) or concentrically arranged (compact b.).

lingual bone  hyoid b.

long bone  a bone that has a longitudinal axis of considerable length, consisting of a body or shaft (the diaphysis) and an expanded portion (the epiphysis) at each end that is usually articular; typically found in the limbs.

lunate bone  the bone in the proximal row of carpal bones lying between the scaphoid and triquetral bones.

malar bone  zygomatic b.

marble bones  osteopetrosis.

mastoid bone  mastoid part of temporal bone; see under part.

metacarpal bones  the five cylindrical bones of the hand (metacarpals), which articulate proximally with the bones of the wrist and distally with the proximal phalanges of the fingers; numbered from that articulating with the phalanx of the thumb to that articulating with the phalanx of the little finger.

metatarsal bones  the five bones (metatarsals) extending from the ankle to the phalanges of the toes; numbered from the most medial articulating with the phalanx of the big toe to the most lateral articulating with the phalanx of the little toe.

nasal bone  either of the two small, oblong bones that together form the bridge of the nose.

navicular bone  the oval-shaped tarsal bone found between the talus and the three cuneiform bones.

occipital bone  a single trapezoid-shaped bone at the posterior inferior part of the cranium, articulating with the two parietal and two temporal bones, the sphenoid bone, and the atlas; it contains a large opening, the foramen magnum.

palatine bone  the irregularly shaped bone forming the posterior part of the hard palate, the lateral wall of the nasal fossa between the medial pterygoid plate and the maxilla, and the posterior part of the floor of the orbit.

parietal bone  either of the two quadrilateral bones forming part of the superior and lateral surfaces of the skull, and joining each other in the midline at the sagittal suture.

pelvic bone  hip b.

petrous bone  petrous part of temporal bone; see under part.

pisiform bone  the medial bone of the proximal row of carpal bones.

pneumatic bone  bone that contains air-filled spaces.

premaxillary bone  premaxilla.

pterygoid bone  see under process.

pubic bone  the anterior inferior part of the hip bone on either side, articulating with its fellow in the anterior midline at the pubic symphysis; it is a separate bone in early life.

rider's bone  localized ossification of the inner aspect of the lower end of the tendon of the adductor muscle of the thigh; sometimes seen in horseback riders.

semilunar bone  lunate b.

sesamoid bones  numerous ovoid nodular bones, often small, usually found embedded within a tendon or joint capsule, principally in the hands and feet; two sesamoid bones, the fabella and patella, are associated with the knee.

shin bone  tibia.

sphenoid bone  a single irregular, wedge-shaped bone at the base of the skull, forming part of the floor of the anterior, middle, and posterior cranial fossae.

squamous bone  squamous part of temporal bone; see under part.

sutural bone  variable and irregularly shaped bones in the sutures between the bones of the skull.

tail bone  coccyx.

tarsal bones  the seven bones of the ankle (tarsus), including the calcaneus, the cuboid bone, the navicular bone, the talus, and the intermediate, lateral, and medial cuneiform bones.

temporal bone  either of the two irregular bones forming part of the lateral surfaces and base of the skull, and containing the organs of hearing. It is divided anatomically into four parts: the mastoid, petrous, squamous, and tympanic parts.

thigh bone  femur.

trapezoid bone  the bone in the distal row of carpal bones lying between the trapezium and the capitate bone.

triquetral bone  the bone in the proximal row of carpal bones lying between the lunate and pisiform bones.

turbinate bone  any of the nasal conchae.

tympanic bone  tympanic part of temporal bone; see under part.

unciform bone , uncinate bone hamate b.

wormian bone  sutural bone.

zygomatic bone  the quadrangular bone of the cheek, articulating with the frontal bone, the maxilla, the zygomatic process of the temporal bone, and the greater wing of the sphenoid bone.

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lacrimal bone

n.

A thin irregularly rectangular plate forming part of the medial wall of the eye socket behind the frontal process of the maxilla.

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lacrimal bone,

one of the smallest and most fragile bones of the face, located at the anterior part of the medial wall of the orbit. It unites with the maxilla to form the groove for the lacrimal sac.

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bone,

n 1. the material of the skeletons of the tissue composing bones.
n 2. dense, hard, and slightly elastic connective tissue in which the fibers are impregnated with a form of calcium phosphate similar to hydroxyapatite.
3. the bones of the human skeleton.
n 4. a single element of the skeleton such as a rib or femur.

bone, alveolar

n the specialized bone structure that contains the alveoli or sockets of the teeth and supports the teeth.

bone, alveolar, architecture,

n the structural pattern of the alveolar bone and its subjacent latticework of supporting bone. The alveolar bone is thin and compact adjacent to the periodontal ligament. The trabecular bone connects and reinforces the individual alveoli. The architecture of a bone is the result of functional stimuli to that bone; the stimuli vary according to type, intensity, and duration.

bone, alveolar, metabolism,

n the metabolic activity occurring within alveolar bone, which is generally slower than that occurring within metaphyseal bone but more rapid than that of diaphyseal bone.

bone apposition,

n See bone deposition.

bone augmentation,

n a procedure used to build or enhance bone. It refers to either bone grafting or bone growing. Bone augmentation materials are classified as osseous, in which bone or bony substitutes are used to form new bone, or osseous conductive, in which these materials provide a platform for regeneration without taking part in actual bone formation.

bone, basal,

n the part of the mandible and maxilla from which the alveolar process develops.

bone, bundle,

n the bone forming the immediate bone attachment of the numerous bundles of collagen fibers of the periodontal ligament that have been incorporated into the bone.

bone bur,

n a drill designed to cut into bone.

bone, cadaver,

n bone that has been donated for medical purposes from one person to another; used especially in bone grafting procedures. See also allogenic and allografts.

bone calcium content,

n the amount of calcium stored in bone tissue. Plasma calcium is in constant exchange with the calcium of the extracellular fluid and bones. The parathyroid gland maintains the constancy of the calcium concentration in the plasma. The bones serve as a reservoir of calcium and phosphate to provide for the other needs of the body and supply minerals for deposition in the skeleton.

bone, cancellous (spongy bone, supporting bone, trabecular bone),

n the bone that forms a trabecular network, surrounds marrow spaces that may contain either fatty or hematopoietic tissue, lies subjacent to the cortical bone, and makes up the main portion of a bone.

bone, cancellous, atrophy of disuse

n the wasting of bone tissue occurring with loss of function of a part (e.g., a tooth). The supporting bone assumes an osteoporotic nature, and the marrow remains fatty or hematopoietic.

bone cells,

n.pl the group includes osteoblasts, osteocytes, osteoclasts, and osteoprogenitor cells.

bone changes, mechanical factors,

n.pl the pressure and tension forces that play an important role in determining bone structure. Improperly controlled appliances can resorb bone faster than deposition can occur, causing mobile teeth and traumatic occlusion. Poor vascularity is a concomitant cause of undue pressure and tension and may inhibit repair and cause necrosis.

bone chips,

n.pl the small pieces of cancellous bone generally used to fill in bony defects and precipitate recalcification.

bone, compact,

n the hard, dense bone composing the outer cortical layer and consisting of periosteal bone, endosteal bone, and haversian systems.

bone conduction,

n See conduction, bone.

bone crest,

n the most coronal portion of alveolar bone.

bone cyst,

n 1. a vascular cyst eccentrically placed within a bone.
n 2. ostitis fibrosa cystica, a parathyroid disorder characterized by cyst formation and the replacement of bone tissue with fibrous connective tissue.

bone defects, angular,

n.pl the usually localized anomalies that occur in the crestal bone as the result of both periodontal inflammation and occlusive trauma.

bone density,

n the compactness of bone tissue. The demonstration of bone density by means of radiographs directly depends on the quantity of inorganic salts contained in the bone tissue.

bone deposition,

n the apposition or formation of new bone as a normal physiologic process.

bone development,

n B See bone, endochondral, formation; bone formation; and bone, intramembranous, formation.

bone, effect of external radiation to,

n damage to the bones of adults is most often seen after heavy and localized radiation treatment.

bone, endochondral

n a bone that is developed in relation to antecedent cartilages (e.g., long bones, mandible). See also bone, intramembranous.

bone, endochondral, formation,

n a replacement of previously formed embryonic cartilage with an adult bony structure. The actual replacement of cartilage by bone is only part of the process, however; much of the bone is laid down directly external to the embryonic cartilage. See also bone, membrane, formation.

bone formation,

n the deposition of an organic mucopolysaccharide matrix (osteoid) that is subsequently mineralized with calcium salts. See also bone apposition and bone deposition.

bone graft, autogenous

n See graft, autogenous bone.

bone graft, donor site,

n See donor site.

bone graft, onlay,

n See graft, onlay bone.

bone graft, recipient site,

n See recipient site.

bone groove,

n an osteotomy into or near the crest of the alveolar ridge for placement of an endosteal blade type of implant.

bone groove, canted,

n an osteotomy sloped to avoid the mandibular canal or keep the implant infrastructure within the medullary confines.

bone, horizontal loss of,

n a resorption of bone caused by periodontal inflammation in which the bone crest remains even with the cementoenamel junctions of two adjoining teeth. The condition may be localized or generalized.

Horizontal bone loss.

bone, internal reconstruction of,

n the formation of bone on the tensional side of the periodontal ligament with concurrent resorption from the marrow space; contralaterally, resorption of alveolar bone with apposition from the endosteum in the marrow space.

bone, interproximal,

n the bone that forms the septa between the teeth; consists primarily of a spongy supporting bone covered by a layer of cortical bone. See also septum, interdental.

bone, intramembranous,

n a bone developed within a membrane but having no associated cartilage (e.g., parietal, frontal, bones of upper face). See also bone, endochondral.

bone, intramembranous, formation,

n membrane bone forms directly from the mesenchyme, first as a thin, flattened, irregular bony plate or membrane in the dermis and gradually expanding at its margins and becoming thickened by the deposition of successive layers of additional bone on the inner and outer surfaces. See also bone, endochondral, formation.

bone involvement,

n changes in the alveolar and supporting bone occurring as a sequel to or accompanying inflammatory or dystrophic disease; usually of a resorptive nature.

n the small, fragile, paired facial bone that helps form a part of the orbital wall and also a small part of the nasal cavity. The bone has four borders and two surfaces that articulate with four other facial bones.

bone lamella,

n bone having the appearance of layers of thin leaves or plates. This appearance is produced by lines representing periods of inactivity of bone formation.

bone, malar (zygomatic bone), frontal process of,

n a prominence on the zygomatic bone (cheekbone) that forms the anterior lateral orbital wall.

n a prominence on the zygomatic bone (cheekbone) that forms part of the inferior rim of the orbit and a small part of the orbital wall.

n a prominence on the inferior aspect of the zygomatic bone (cheekbone) that articulates with the zygomatic process of temporal bone to form the zygomatic arch.

bone, marble,

n See osteopetrosis.

bone marrow,

n the soft vascular tissue that fills bone cavities and cancellous bone spaces and consists primarily of fat cells, hematopoietic cells, and osteogenetic reticular cells.

bone marrow transplant,

n the transplantation of bone marrow from healthy donors to stimulate production of formed blood cells. It is used in treatment of hematopoietic or lymphoreticular diseases such as aplastic anemia, leukemia, immune deficiency syndromes, and acute radiation syndrome.

bone membranes,

n.pl the membrane structures associated with the growth, development, and repair of bone. They include the periosteum, a connective tissue layer adjacent to bone surfaces; periodontal ligament, a modified periosteum associated with tooth structure; and endosteum, a thin layer of connective tissue lining the walls of the bone marrow spaces.

bone, microscopic appearance of,

n the composition of bone tissue as viewed under a microscope. Microscopically, bone is composed of osteocytes embedded within lacunae in a calcified intercellular matrix. Extending from the lacunae are small canals called canaliculi, which communicate with canaliculi of adjacent lacunae. Through this system of canals, nutrient material reaches the osteocytes and provides avenues for the removal of waste products of metabolism. It is deposited in incremental layers (lamellae) around haversian canals, the lamellae toward the surface of the bone being more or less parallel to it.

bone mineral content, chemistry of,

n the hardness of bone results from its mineral content in the organic matrix. The minerals (commonly designated as bone salts) and the organic matrix make up the interstitial substance of bone. The bone salts consist essentially of hydroxyapatite (Ca₁₀[PO₄]₆[OH₂]), carbon dioxide, and water, with small amounts of other ions.

bone morphogenetic protein (BMP),

n See protein, bone morphogenetic (BMP).

bone, normal level of,

n the distance from the interdental bone crest to the cementoenamel junction in healthy teeth, usually 1 to 1.5 mm.

n the saucer-shaped cranial bone that forms the most posterior part of the skull; the spinal cord passes through the foramen magnum, an opening at its base.

bone onlay,

n See graft, onlay bone.

bone, perichondrial

n bone that is deposited in concentric layers around the long shaft of the bone in a manner similar to that of the growth of endochondral bone.

bone, physical properties of,

n a compact bone has the following physical characteristics: specific gravity, 1.92 to 1.99; tensile strength, 13,000 to 17,000 psi; compressive strength, 18,000 to 24,000 psi; compressive strength parallel to the long axis, 7150 psi; compressive strength at right angles to the long axis, 10,800 psi. These physical characteristics make bone particularly suitable for carrying out its functions of weight bearing, leverage, and protection of vulnerable viscera.

bone rarefaction

n a decreased density of bone such as a decrease in weight per unit of volume.

bone recession,

n See recession, bone.

bone, resorption and repair of,

n an adaptive physiologic mechanism occurring as long as the individual retains the natural dentition. See also resorption of bone.

bone, resting lines in,

n.pl the regular lines created by alternating periods of bone formation and rest, giving a tierlike appearance to lamellar bone.

bone, reversal lines in,

n.pl the irregular lines containing concavities directed away from the bundle bone and serving as histologic indications that resorption has taken place up to that line from the marrow side.

bone sequestrum,

n See sequestrum.

bone, spongy,

n See bone, cancellous.

bone support,

n the amount of alveolar and trabecular bone adjacent to a tooth that can provide attachment, investment, and support for the tooth.

bone, supporting,

n See bone, cancellous.

bone, supporting, atrophy of disuse,

n See bone, cancellous, atrophy of disuse.

bone surgery,

n See surgery, osseous.

bone, thickened margin of,

n the widening of the crest of the alveolus, primarily on the buccal and lingual aspects, varying from a thick ledge to a “beading” of the bone margin; results in a more or less bulbous contour of the gingival tissue overlying it.

bone, trabecular

n See bone, cancellous.

bone, vertical loss of,

n a resorption of bone caused by periodontal inflammation and occlusal trauma in which the bone crest is below the cementoenamel junctions of two adjoining teeth. It can be localized (mainly) or generalized.

bone, vertical plates of the palatine,

n the thin, oblong-shaped bone with two surfaces and four borders. It helps to form the floor of the orbit, the outer wall of the nasal cavity, and several adjoining structures.

bone volume (mass), age-affecting,

n decreases that occur in human body bone mass after age 40. Diet and exercise may be contributing factors.

bone wax,

n See wax, bone.

bone, woven,

n a character and pattern of bone resulting from the interweaving of broad bands of bone.

bone(s), cranial,

n the eight bones that make up the skull and protect the brain and include the ethmoid, frontal, occipital, sphenoid, two parietal, and two temporal bones.

bone(s), facial,

n the 14 bones that include the mandible, maxilla, frontal bones, nasal bones, and zygoma. With the exception of the mandible, maxilla, and vomer bones, the bones of the face occur in pairs, thus accounting for facial symmetry. They provide the framework for the face, serve as entry points for the digestive and respiratory systems, and provide the attachments for the muscles controlling facial expression.

bone(s), horizontal plates of palatine,

n the bones that form the posterior part of the hard palate and consist of four borders and two surfaces.

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orbit 

A rigid bony cavity in the skull which contains an eyeball, orbital fat, the extraocular muscles, the optic nerve, nerves and blood vessels, lacrimal system and fibrous tissue of various kinds. This packing serves to keep the eyeball reasonably well fixed in place as it rotates. The orbital cavity has the approximate form of a pyramid. The walls of the orbital cavity are formed by seven bones. The medial wall of the orbit consists of: (1) the frontal process of the maxilla (maxillary); (2) the lacrimal bone; (3) the lamina papyracea of the ethmoid; and (4) a small part of the body of the sphenoid. The floor of the orbit consists of: (1) the orbital plate of the maxilla; (2) the orbital surface of the zygomatic (malar) bone and (3) the orbital process of the palatine bone. The lateral wall of the orbit consists of (1) the orbital surface of the greater wing of the sphenoid, and (2) the orbital surface of the zygomatic. The roof of the orbit is made up mainly by the frontal bone and behind this by the lesser wing of the sphenoid. The orbit is lined with a membrane of tissue called the periorbita (or orbital periosteum) which extends to the orbital margin (anterior rim of the orbit) where it becomes continuous with the periosteum covering the facial bones. The periorbita is loosely attached to the bones except at sutures, foramina and the orbital margin where it is firmly attached. The bones are much thicker at the margin (rim) than they are along the walls of the orbital cavity. There are many apertures and gaps in the orbit through which blood vessels and nerves pass (see Table O4). See orbital axis; optic canal; inferior orbital fissure; superior orbital fissure; orbital fracture; cavernous haemangioma; lamina papyracea.

Table O3 Bones forming the walls of the orbit
roof	medial wall
1. frontal	1. maxilla
2. lesser wing of sphenoid	2. lacrimal
	3. ethmoid
	4. sphenoid
floor	lateral wall
1. maxilla	1. greater wing of sphenoid
2. zygomatic
3. palatine	2. zygomatic

Table O4 Orbital apertures
aperture	location	contents
optic canal	at the apex (in lesser sphenoid)	optic nerve ophthalmic artery sympathetic nerve fibres
superior orbital fissure	at the apex (gap between greater and lesser sphenoid)	III, IV, V, VI nerves sympathetic nerve fibres ophthalmic vein recurrent lacrimal artery
inferior orbital fissure	between lateral wall and posterior part of the floor	infraorbital nerve zygomatic nerve branch of inferior ophthalmic vein nerve fibres from the pterygopalatine (sphenopalatine) ganglion to orbital periosteum
ethmoidal foramina (anterior and post.)	medial wall (frontal/ethmoidal suture)	ethmoidal vessels ethmoidal nerve/external nasal nerve
zygomatic foramen	lateral wall	zygomatic nerve and vessels
nasolacrimal canal	medial wall (maxilla/lacrimal)	nasolacrimal duct